I highly recommend Corsair or Crucial. For years I have used their stuff and I've never had a single problem with their products. They are more expensive than some stuff you can get, but you get a very high quality product.

In my new MacBook I wanted to upgrade the RAM from the get go and didn't plan ahead to order it online (silly me). I went with Patriot memory from Fry's and have had no complaints. Patriot is cheaper than Corsair or Crucial but they're also a newer player.